1. Field of the Invention
The present invention relates to golf balls. More particularly, the present invention relates to multi piece golf balls having a core, a mid layer and a cover.
2. Description of the Related Art
Top concern to golf players for golf balls is their flight performances. The golf players particularly place great importance on flight distance attained upon shots with a driver. The golf players also place great importance on flight distance attained upon shots with a long iron and a middle iron.
Golf players also place great importance on spin performances of golf balls. Great back spin rate results in small run. For golf players, golf balls which are liable to be spun backwards are apt to be rendered to stop at a targeted position. Great side spin rate results in easily curved trajectory of the golf ball. For golf players, golf balls which are liable to be spun sidewise are apt to allow their trajectory to curve intentionally. Golf balls that are excellent in spin performances are excellent in control performances. High-level golf players particularly place great importance on control performances upon shots with a short iron.
For golf players, durability of golf balls is also important. Golf balls that are not damaged by repeated hitting have been desired. Further, golf balls that are resistant to generation of cuts and wrinkles on the cover upon full shots with a short iron have been desired.
In light of the flight performances, control performances and durability, golf balls having a variety of structures have been proposed. For example, U.S. Pat. No. 6,106,415 discloses a golf ball having a core, a mid layer comprising an ionomer resin and a cover comprising polyurethane.
Golf balls have numerous dimples on the surface thereof. The dimples cause turbulent flow separation through disrupting the air flow around the golf ball during the flight. By causing the turbulent flow separation, a separating point of air from the golf ball shifts backwards leading to the reduction of a drag. The turbulent flow separation promotes the differentia between upper separating point and lower separating point of the golf ball, which results from the backspin, thereby enhancing the lift force that acts upon the golf ball.
Covers having high elasticity are advantageous in terms of the flight performance. However, highly elastic covers liable to deteriorate the control performance. Soft covers are advantageous in terms of the control performance. However, soft covers are disadvantageous in terms of the flight performance and durability. Demands from the golf players for golf balls have increasingly escalated in recent years. Highly balanced flight performances, control performances and durability have been desired. An object of the present invention is to provide golf balls that are excellent in flight performances, control performances and durability.